Evaluate the statement: “Thyristors are suitable for DC circuit breakers but not for AC circuit breakers.”

Introduction / Context:
Using thyristors (SCRs) as part of static switching or breaker arrangements depends on how easily the current can be interrupted. AC systems feature natural current zeros, whereas DC systems do not, making turn-off and fault interruption fundamentally different challenges.

Given Data / Assumptions:

• Thyristors latch on and require current to drop below holding current for turn-off.
• AC circuits have natural current zero crossings; DC circuits do not.
• Statement claims suitability for DC but not for AC.

Concept / Approach:

In AC, the current naturally passes through zero each half-cycle, aiding commutation of SCRs. In DC, forced commutation or auxiliary circuitry is needed to turn off an SCR, complicating design. Therefore, thyristor-based breakers are generally easier to realize in AC (not DC), contrary to the statement.

Step-by-Step Reasoning:

Verification / Alternative check:

Industrial practice: AC solid-state relays with SCRs are common; DC solid-state breakers typically use MOSFETs/IGBTs or complex forced-commutation if SCRs are used.

Why Other Options Are Wrong:

• True/conditional truths: contradict the physics of commutation.
• Depends solely on gate current: turn-off is not controlled by gate current in standard SCRs.

Common Pitfalls:

• Assuming a gate signal can turn an SCR off—it cannot in conventional devices.
• Overlooking the role of natural current zero in AC.

Final Answer:

False